Sometimes when installing drywall you come across joints that are slightly uneven. This is due to either slight miscalculations in framing, warped studs or two different thicknesses of drywall. Taping these types of joint takes a little more work. This is because it is necessary to build up the joint properly. Taping drywall if it is uneven requires a few days to accomplish because of the building up process. Done correctly and the wall will look even across the room.
Fill a drywall pan with joint compound. Load a 6-inch drywall knife with compound and spread the compound in an even layer over the joint. The compound should extend up to six inches on each side of the joint.
Place the end of the drywall tape at one end of the joint with the crease side pointing toward the wall. Press the tape over the joint and down the length of the joint. Tear the tape off the roll.
Run an 8-inch drywall knife across the top of the tape at an angle from the top down to the bottom. Uses light pressure when dragging the knife across the tape because you want to force the compound to squeeze out of the edges of the tape. This flattens the tape against the wall and removes bubbles.
Spread a second layer of compound over the joint with the 8-inch drywall knife. Feather the compound away from the joint as you apply it to the wall. Allow the compound one day to dry completely.
Apply a third layer of compound, thicker than the previous two layers, to the uneven joint with a 10-inch drywall knife once the first two coats are thoroughly dry. Spread from the high side of the uneven joint to the low side, applying more compound as necessary on the low side to blend in with the high side. This builds up the uneven joint and blends in smoother when sanding. The 10-inch knife allows the compound to be applied in a more even manner across a wider area. Allow the third coat of compound to dry thoroughly. Thorough drying usually takes at least one day.
Install 120-grit sandpaper into a hand sander. A hand sander is basically a flat piece of metal with a handle. The sandpaper fits under clamps on the top of the flat plate. Ensure the sandpaper is tight when tighten the clamps on the hand sander.
Sand the compound in a back and forth motion applying light pressure. Once the compound is smooth and even, place the edge of a 12-inch drywall knife across the joint. Attempt to rock the blade back and forth. The blade edge should be against the wall across the entire length of the blade. If you can rock the blade, sand the high side more with a sanding sponge.